These rugged and dependable boats provided yeoman service during World War II, along with their immediate successors, the similar Sargo class.

[7] Authorized under the Fiscal Year 1936 provision of the Vinson-Trammell Act,[8] two distinct, but very similar, designs were developed, to be built by three different constructors.

Using the Portsmouth plans and acting as a follow yard, the Mare Island Naval Shipyard of Vallejo, California built Sturgeon (SS-187).

[9] The two designs differed in minor details such as the locations of the access hatches for the forward engine room and crew's quarters, the shape of the horizontal conning tower cylinder, and, most significantly, the closure of the main induction valve.

Portsmouth and Mare Island ran into production difficulties with their conning towers, discovering cracks that caused the cylinder to fail the required pressure test.

The problem was successfully fixed, but the experience caused the government yards to adopt the double concave design for the next several years.

[11] Externally, there were minor differences in the shape of the upper edge of the aft end of the conning tower fairwater.

[15] The development of the Torpedo Data Computer, making broadside attacks practical, had made stern tubes more desirable.

The impracticality of spending several hours on the surface in enemy waters moving torpedoes below was lost on the designers.

Steady development work by GM-Winton had largely corrected earlier problems and this engine proved to be fairly reliable and rugged.

Reluctant to give up on the promise of the engine, the Navy coddled the HORs along until after the United States entered the Pacific War following the attack on Pearl Harbor, when increased funding and operational needs caused these engines to be replaced with GM-Winton 16-278As during the boat's first wartime overhauls.

For submerged operation, the direct drive engines were declutched from the reduction gears and the motors drove the shafts with electricity supplied by the batteries.

They transferred to the Pacific Fleet in late 1939, homeported out of San Diego, commanded by COMSUBPAC Admiral Wilhelm L.

[25] In October 1941, as war clouds loomed on the horizon, all the Salmons and most other newer available submarines were transferred to the Asiatic Fleet as part of a belated effort to reinforce U.S. and Allied forces in the Philippines.

The Japanese occupation of southern Indo-China and the August 1941 American-British-Dutch retaliatory oil embargo had raised international tensions.

It was found that portions of the fairwater plating could be cut away both fore and aft of the bridge, greatly reducing the silhouette.

This also had the desirable effect of creating mounting locations for 20mm Oerlikon autocannons, which were useful against aircraft and small surface targets.

It was replaced by the Mark 9 4-inch (102 mm)/50 caliber gun in 1943–44, in most cases removed from an S-boat being transferred to training duty.